A RuO2 -SnO2 mixed metal oxides electrode was investigated. The results showed that it has a good activity and selectivity for C12 evolution electrocatalysis in NaCl solution. By means of XPS the surface composition of electrode was studied. It was found that Ru content and adsorbed chlorine of DSA (Ru -Sn) was higher than DSA (Ru -Ti). Potentiometric titration was used to characterize the acid - base properties of the surface of mixed electrodes. PZC and APZC obtained suggested that DSA (Ru -Sn) surface has stronger acidity and more specific adsorption of Cl . The electrocataysis behavior of mixed metal oxides electrode is in a close relationship with surface composition and properties.